Abstract: In order to obtain entomogenous fungi strains with high toxicity against Q-biotype Bemisia tabaci and apply it to the production, the toxicity of Beauveria bassiana strain against Q-biotype B. tabaci were measured by using the method of spray. And the time-dose-mortality (TDM) model was applied to analyze the time and dose effects of strain Bb84 on Q-biotype B. tabaci. The results showed that the mortality rate of strain Bb84 against the 3rd nymph was the highest and its lethality was the highest among the five tested strains and the daily cumulative mortality increased with the concentrate of conidial suspension. Strain Bb84 also had high toxicity to the 2nd and 4th nymph. The analysis of TDM model showed that the LC 50 value decreased and dose effect increased with the extension of time; LT 50 values were 5.44, 4.61 and 4.05 d for the 3rd nymph of B. tabaci at spore concentrations of 1.0×107, 1.0×108 and 1.0×109 spores/mL, respectively. Thus the LT50 value decreased and time effect increased with the extension of dose. Therefore, in the actual production, when the concentration of the B. bassiana strain Bb84 is higher than 1.0×108 spores/mL, the control effect of the 3rd nymph of B. tabaci is better.